Gear with bearing arrangement

ABSTRACT

A gear including a frame, a first shaft, a first gearwheel arranged on the first shaft and in engagement with a second gearwheel mounted on a second shaft, the second shaft including bearings at both sides of the second gearwheel between the frame and the second shaft. The second shaft revolves about the bearings placed on each side of the second gearwheel. At least one spring is fitted to act with a force upon an outer race of rolling members of one of the bearings. A glide fitting is provided between a circumferential face of the outer race and the gear frame or a connected part. The force effect applied by the spring(s) is transferred through the rolling members of the bearing to the inner race of the bearing and further to the other bearing placed at the opposite side of the gearwheel whereby the play in both bearings between the rolling members and the bearing races is eliminated.

FIELD OF THE INVENTION

The invention concerns a gear.

BACKGROUND OF THE INVENTION

From the prior art, minimization of the bearing play is known by using aseparate transfer mechanism, a screw device, by whose means the play isminimized by shifting the bearing race in the lateral direction. In theprior-art solutions, the shifting of the bearing race takes placeexpressly by means of a separate positioning actuator.

OBJECTS AND SUMMARY OF THE INVENTION

In the present patent application, attempts have been made to find asolution for the problem of bearing play, in particular in a gear inwhich the gear comprises a high-speed shaft and a low-speed shaft, inwhich connection the high-speed shaft is fitted to rotate the low-speedshaft. The low-speed shaft is mounted from both sides of the toothed rimby means of rolling ball bearings. In a prior-art solution of said sort,in particular with increasing speeds, problems arise in the bearings ofthe low-speed shaft. In particular in paper machine drives, whentemperatures vary, the bearing plays must be adequate in order that areliable operation of the bearing could be guaranteed under allconditions of operation. In a gear, it is possible to speak of a loadeffect point at the point at which the high-speed shaft is in contactwith the low-speed shaft. In a normal situation of loading, attempts aremade to minimize the forces applied to the bearings by balancing thegear by means of a torque support from a suitable point on the outsideframe constructions. When the balancing is successful, the bearing fullyrelies on its plays and is, in such a case, susceptible of oscillation.In such a case, outside impulses produce an increased risk of damage inthe bearing means. When the gear is used in a paper machine drive, highchanges in the thermal load arise on the grooved ball bearings placed atboth sides of the gearwheel of the low-speed shaft, which changesfurther result in a requirement of a large play. When the play becomeslarger, some of the rolls glide along the race track, in which casebearing damage and bearing wear are increased. According to the presentinvention, the service life of the bearings of the low-speed shaft hasbeen increased by using a separate spring device in the lateral shiftingof the bearings. The spring device is fitted so that its springs actupon the bearings of one of the bearing races, so that the spring forceis applied outwards from the area between the bearings and upon theouter bearing race. The bearing race is mounted by means of a glidefitting on the frame of the bearing housing, and by means of the springsthe bearing race is shifted outwards in the construction. In this waythe bearing play is eliminated and the rolling members are shifted intocontact with their bearing races, both with the inner bearing race andwith the outer bearing race. When the rolling members are shifted intocontact with the inner bearing race, the force acts upon the gearwheelshaft connected with the inner bearing race, and the inner race of theother bearing is now further shifted, in its turn, so that the shiftingtakes place towards the vertical central axis Y of the bearing. Thus, bymeans of the same spring device, the plays are eliminated from two setsof bearing means, both from one side and from the other side of thegearwheel.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be described in the following with reference to somepreferred embodiments of the invention illustrated in the figures in theaccompanying drawings, the invention being, however, not to be confinedto said embodiments alone.

FIG. 1 illustrates the situation occurring at the load effect point in abearing construction.

FIG. 2A is a sectional view of a gear construction in accordance withthe present invention.

FIG. 2B is a separate illustration of a ring with spring sockets inaccordance with the present invention.

FIG. 2C is a sectional view taken along the line I--I in FIG. 2B.

FIG. 2D is an illustration in part of the fixing of the ring with springsockets to the gear frame.

FIGS. 3A, 3B, 3C and 3D show different bearing constructions which aresuitable for use in a gear in accordance with the present invention andin a spring loading in accordance with the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 illustrates the situation caused by the load effect point inparticular in bearing constructions of large, 500 mm . . . 800 mm,diameter. In the prior-art situation shown in FIG. 1, the load acts uponthe point P. The direction of effect of the force is indicated by thearrow F₁. In such a case, the play is at the minimum at the sideopposite to the load (point O₁) and at the maximum at the side of theload (point O₂). The rolling members in the bearings glide (at the pointO₂) and do not revolve along their race track faces. This furtherresults in wear and possibly in bearing damage. The situation is madeworse, in particular with large bearing diameters (φ 500 mm . . . φ 800mm), especially by the fact that the bearing play must be relativelylarge in order that the variations occurring in the thermal load couldbe taken into account. When the play is large between the rollingmembers and the bearing rings or races in the bearing construction, asituation is also possible in which, when the gear is well balanced bymeans of a torque arm, oscillations further cause resonance in thebearing members. In such a case, the susceptibility of the bearings todamage is increased further.

FIG. 2A illustrates a gear in accordance with the present invention. Thegear 10 comprises a frame 11. The drive is introduced into the gearthrough the shaft 12. The shaft 12 is mounted from both sides of itsgearwheel 13 by means of bearing means 14 and 15. The high-speed shaft12 is fitted to rotate the shaft 16 comprising the gearwheel of largerdiameter. The shaft 16 comprises the gearwheel 17 and the bearing means18 and 19 at both sides. The bearing means 18 and 19 can be grooved ballbearings, tapered roller bearings or angular-contact ball bearings. Theyare preferably single-row bearings, which means that the bearing membersare placed in one row only between the inner race and the outer race ofthe bearing. Each bearing 18,19 comprises rolling members 20a₁ such asrollers, balls or equivalent, between its races, i.e. the inner race andthe outer race. The rolling members run in the inner circumferentialgrooves in their bearing races.

According to the invention, the construction is provided with springmeans, which comprise a ring 21 with spring sockets, and in thedifferent spring sockets 22a₁, in the ring 21 there are the springs 23a₁preferably spiral springs. The ring 21 with spring sockets is attachedto the side face 11a₁ of the gear frame 11 by means of screws 24a₁.Thus, the ring 21 with spring sockets is placed between the side face11a and the side face D₁ of the gear wheel 17 placed on the shaft 16.Thus, the springs 23a₁ of the ring 21 with spring sockets are fitted toact with a force outwards from the vertical centre line (Y line) of thebearing construction (force arrows in the direction L₁ and in thedirection of the axis X₁ of rotation). The construction is fitted insuch a way in relation to the outer race of the bearing 18 that the ring21 with spring sockets is fixed by means of screws 24a₁ to the frame 11above the side face C₁ of the outer race 18' of the bearing so that thesprings 23a₁ press the race 18' with a force and act upon its frontface. The circumferential face C₁ of the outer race 18' of the bearing18 is fitted with a glide fitting on the frame 11 of the gear. Then, thebearing race 18' can be displaced in the direction of the axis ofrotation (X₁ axis) of the gear so that the rolling members 20a₁ of thebearing can be brought into contact both with the side face of the innerrolling groove of the outer race 18' of the bearing and with the sideface of the inner rolling groove of the inner race 18" of the bearing.Thus, as is shown in the figure, the force F acts in the direction L₁and shifts the rolling members 20a₁ of the bearing means into contactboth with the side of the rolling groove of the outer race 18' of thebearing 18 and with the side face of the rolling groove of the innerrace 18" of said bearing. Thus, the plays between the rolling members20a₁ of the bearing and the bearing races 18',18" have been eliminated.Thus, the force effect is transferred from the outer race 18' further tothe inner race 18" and further to the shaft 16, which is also shifted inthe direction L₁.In this connection, the force acts upon the inner race19" of the second bearing means 19, and thereby the play is alsoeliminated in said second bearing 19 of the shaft. It is an essentialfeature that the shaft 16 is floating, i.e. freely moving in its axialdirection (direction X₁). The bearing 19 is fixed to the gear so thatboth the inner race 19" of the bearing 19 is fitted on the shaft 16 witha press fitting, i.e. stationarily, and the outer race 19' of thebearing 19 is mounted stationarily on the connected gear construction11, preferably likewise with a press fitting. However, since the shaft16 can be displaced in the direction of the central axis and axis ofrotation (X₁ axis) of the shaft 16, by means of the force F it is alsopossible to shift the rolling members 20a₁ of the bearing against theside faces of the inner rolling grooves or rolling tracks of theirbearing races 19' and 19". Thus, in this connection, by means of thesprings 23a₁, it is possible to eliminate the play also in respect ofthe second bearing means.

Thus, it is not at all self-evident in what area of the bearing meansthe force F of the springs 23a₁ is fitted to act, or in what directionin relation to the vertical central axis (Y axis) of the gear. In theconstruction in accordance with the invention, the springs 23a₁ act upontwo sets of bearing means at both sides of the gearwheel 17 on the shaft16 in the gear 10. According to the invention, when the force F iseffective away from the Y axis in the direction of the central axis ofrotation (X axis) of the gear, the bearing means are brought into a whatis called O position, in stead of the other alternative, i.e. the Xposition. In the so-called O position, the rolling axes of the bearingmeans are placed circumferentially, and, on the other hand, in the Xposition the rolling axes of the bearing means are placed so that therolling axes intersect each other in the centre point of thejournalling. From the point of view of the stability of the journalling,said so-called O position is preferable. In the construction inaccordance with the invention, when the spring means act outwards fromthe vertical centre line (Y line) of the gear and when the spring meansact expressly upon the outer bearing race, the so-called O position isaccomplished in the journalling. The vertical centre line Y passesthrough the middle of the gearwheel 17 perpendicularly to the axis X₁ ofrotation.

FIG. 2B is a separate illustration of the ring 21 with spring sockets asa side view. FIG. 2C is a sectional view taken along the line I--I inFIG. 2B. The ring 21 with spring sockets is fitted in the area betweenthe bearing means 18 and the gearwheel 17 so that the spring sockets22a₁ in the ring 21 with the spring sockets are opened outwards, inwhich case the springs 23a₁ fitted in the spring sockets 22a₁,preferably spiral springs, cup springs, or equivalent, are fitted to actwith a force F upon the outer race 18' of the bearing means, which outerrace is fitted to the gear or to a connected construction with a glidefitting. The ring 21 with spring cavities includes holes 25a₁ throughwhich the fastening screws 24a₁ are passed and threaded further into thethreaded holes provided in the side face 11a₁ of the frame 11 of thegear. The springs 23a₁ are dimensioned so that normal thermal expansiondoes not produce an excessive additional load on the bearings but, onthe other hand, the spring force is sufficient to prevent gliding(stopping) of the bearing rollers in a situation of operation.

FIG. 2D shows an alternative of fixing the ring with spring sockets tothe frame by means of screws 24a₁ which have been passed through theholes 25a₁,25a₂ . . . into the threaded holes 26a₁ in the frame.

FIG. 3A shows a conventional grooved ball bearing, which can be used inthe journalling in accordance with the present invention and whose outerrace can be acted upon by means of the spring loading device of theinvention. In FIG. 3A, the point of effect and the direction of effectof the spring force are indicated by the arrow F. Thus, the bearingmeans 20a₁ are shifted into contact both with the side face f₁ of therace track e₁ of the outer race 18' of the bearing and with the sideface f₂ of the race track e₂ of the inner race 18" of the bearing. Thus,the play is eliminated between the bearing members 20a₁ and the relatedbearing races 18' and 18". In FIG. 3C a tapered roller bearing is shown,to which the invention is also applicable. FIG. 3B shows anangular-contact ball bearing, for which the invention is also suitable,as it is for the double-row bearing shown in FIG. 3D. By means of thespring rim, forces of about 3000 . . . 5000 N are transferred to theouter ring of the bearing, i.e. to the outer bearing race, when thebearing diameter is in the range of φ 500 mm . . . 800 mm.

What is claimed is:
 1. A gear, which comprises a shaft (12) and on it agearwheel (13), which is in engagement with a gearwheel (17) mounted ona shaft (16), and that the shaft (16) comprises first and secondbearings (18 and 19) arranged along opposite sides of the gearwheel (17)between the frame (11) and the shaft (16), on which bearings the shaft(16) is fitted to revolve, characterized in that the gear comprises atleast one spring fitted to act with a force (F) upon an outer race (18')of said first bearing (18); rolling members (20a₁) arranged between aninner race (18") of said first bearing (18) and said outer race (18') tothereby define a glide fitting arranged between a circumferential face(C₁) of said outer race (18') and said frame (11), whereby a force istransferred through the rolling members (20a₁, 20a₂ . . . ) of saidfirst bearing (18) to the inner race (18") of the bearing (18) andfurther to said second bearing (19) arranged along the opposite side ofthe gearwheel (17), and the play in the first and second bearings (18and 19) arranged along opposite sides of the gearwheel (17), between therolling members and the bearing (18, 19) races (18, 18";19', 19"), iseliminated.
 2. A gear as claimed in claim 1, further comprising a ring(21) having a plurality of spring sockets and wherein said at least onespring comprises a plurality of spiral springs or cup springs each onesaid spiral springs or cup springs being arranged in one of said springsockets, said plurality of spiral springs or cup springs being arrangedto act with a force (F) away and outwards from a vertical center line (Yline) of said first bearing.
 3. A gear as claimed in claim 2, whereinsaid ring (21) having a plurality of spring sockets comprises aplurality of screws and a plurality of corresponding holes equallyspaced about a circumference of said ring, through which each of saidholes one of said plurality of screws pass and are threaded into one ofa plurality of threaded holes in the gear frame.
 4. A gear as claimed inclaim 1, characterized in that the said second bearing (19) isstructured and arranged in such a way that both the inner race (19") andthe outer race (19') of the bearings are in stationary positions inrelation to the gear constructions connected with them.
 5. A gear asclaimed in claim 2, characterized in that said ring (21) having aplrality of spring sockets is connected to the gear frame (11) by meansof screws between the side face (11a₁) of the gear frame and the sideface (D₁) ofthe gearwheel (17) on the rotatable shaft (16).
 6. A gear asclaimed in claim 1, characterized in that the first bearing (18) uponwhich the said at least one spring is fitted so on the gear frame (11)so that said glide fitting is defined between the circumferential face(C₁) ofthe outer race (18') of the first bearing (18) and the gear frame(11), and that the inner race (18") of the first bearing is fittedfixedly on the shaft (16).
 7. In a gear including a frame, a firstshaft, a first gearwheel arranged on the first shaft, a second shaft, asecond gearwheel arranged on said second shaft and in engagement withthe first gearwheel and first and second bearings arranged on arespective first and second side of the second gearwheel between theframe and the second shaft for revolvingly supporting the second shaftrelative to the frame, the improvement comprising:the first bearingincluding an inner race adjacent the second shaft, an outer raceadjacent an opposed surface of the frame and rolling members arrangedbetween said inner race and said outer race, said outer race having acircumferential face movable relative to the opposed surface of theframe to thereby define a glide fitting between said outer race and theopposed surface of the frame, the second bearing including an inner raceadjacent the second shaft, an outer race adjacent an opposed surface ofthe frame and rolling members arranged between said inner race and saidouter race, and at least one spring arranged to provide a force uponsaid outer race of the first bearing to enable movement of said outerrace relative to the frame, whereby the force is transferred throughsaid rolling members of the first bearing to said inner race of thefirst bearing and further to the second bearing such that any play inthe first and second bearings between the rolling members and therespective inner and outer races is eliminated.
 8. The gear of claim 7,wherein said at least one spring is selected from a group consisting ofa spiral spring and a cup spring.
 9. The gear of claim 7, furthercomprising a ring surrounding the second shaft, said ring defining atleast one spring socket for housing a respective one of said at leastone spring.
 10. The gear of claim 9, further comprising connecting meansfor connecting said ring to the frame.
 11. The gear of claim 10, whereinsaid connecting means comprise screws arranged between a side face ofthe frame and a side face of the second gearwheel.
 12. The gear of claim9, wherein each of said at least one spring is a spiral spring.
 13. Thegear of claim 9, wherein said ring includes holes equally spaced about acircumference of said ring, further comprising screws passing throughsaid holes for connecting said ring to the frame.
 14. The gear of claim7, wherein said at least one spring comprises a plurality of springs,further comprising a ring surrounding the second shaft, said ringdefining a plurality of spring sockets each housing a respective one ofsaid springs.
 15. The gear of claim 7, wherein said at least one springis arranged to act with a force away and outward from a vertical centerline of the first bearing.
 16. The gear of claim 7, wherein said innerrace of the second bearing is fixed to the second shaft and said outerrace of the second bearing is fixed to the frame.
 17. The gear of claim7, wherein said inner face of the first bearing is fixedly mounted tothe second shaft.
 18. The gear of claim 7, wherein the first and secondbearings are angular-contact ball bearings.
 19. The gear of claim 7,wherein the first and second bearings are tapered roller bearings.